The invention relates generally to traveling water screens for filtering debris and fish from a stream of water and, more particularly, to a traveling water screen made from a modular conveyor belt.
Many industrial processes use water from rivers, lakes, and oceans. Water taken into an industrial plant must be filtered to prevent debris from fouling equipment and causing damage. Water screens filter out and often remove debris from an influent stream before the debris can enter the plant. But the flow of the influent stream can cause fish to impinge on the face of the screen. Fish that are impinged too long eventually die. Consequently, various approaches are used to recover fish impinged on a water screen.
In one approach, a large curved bucket flight is attached to a vertically moving screen. The bucket is designed so that water flows above and below it and through the traveling screen. Fish are trapped in the bucket in a region of reduced water velocity. Trapped fish and debris are lifted vertically out of the water by the moving screen. As the screen goes around the top of its path, fish and debris are washed out with low and high pressure water.
According to yet another approach, a vertical screen with circular elements similar to conveyors commonly seen at baggage claim areas in airports is used. Each circular element is, itself, a moving screen. A scoop is integral to each circular element. The circular elements rise vertically out of the water and over a drive shaft and sprockets. As the circular elements round the drive shaft, the scoops pour fish and debris into a discharge trough.
But each of these approaches can result in high fish mortality rates. First, fish and debris are mixed and may be difficult to separate. Second, in all these approaches, the fish are handled roughly. The fish are pulled out of the water or sprayed under pressure.
Consequently, there is a need for a water screen system that increases fish survivability.